Phosphorus-containing motor fuel



Uited States Patent 3,060,009 PHOSPHORUS-CONTAINING MOTOR FUEL Edwin 0. Hook, Chagrin Falls, and David P. Tate,

Northfield, Ohio, assignors to The Standard Oil Cornpany, Cleveland, Ohio, a corporation of Ohio No Drawing. Filed June 4, 1959, Ser. No. 817,997 1 Claim. (Cl. 44-69) This invention relates to improved motor fuel compositions and particularly to leaded fuel compositions for high compression, spark-ignition engines which contain organic phosphorus compounds.

It is a Well-recognized fact today that during the operation of an initially clean internal combustion engine on gasoline-type fuels deposits form progressively and accumulate on the Walls of the combustion chamber and on the terminals of sparkplugs. These deposits cause plug fouling, raise octane number requirement of the engine, and in general reduce appreciably the efficiency of the engine. The deposit problem is particularly aggravated when tetraethyl lead is contained in the fuel since the deposits now have a metallic nature which manifests a more harmful effect on engine operation than deposits which are essentially of carbonaceous character. In order to obtain a high octane number fuel such as is required for modern high compression internal combustion engines, most fuels require the addition of tetraethyl lead and hence the deposit problem in the combustion zone becomes aggravated.

A number of compounds of phosphorus have been proposed in the past for addition to gasoline to alleviate these adverse effects of deposits and particularly lead deposits which form in the combustion zone of the engine. One of the chief objections to the use of such phosphorus compounds, however, is that they characteristically lower to some extent the octane number of the fuel which obviously negates in part the advantage gained in the first instance when tetraethyl lead is added to the fuel.

In accordance with the present invention, a class of phosphorus compounds has been found which, when added to a gasoline in amounts to supply the quantity of elemental phosphorus normally required to alleviate the adverse effects on deposit problems, quite surprisingly increases the octane number of the fuel. These compounds may be described as gasoline-soluble organophosphoramides having the following general formula:

wherein R may be hydrogen or an alkyl group containing up to 20 carbon atoms; X may be hydrogen o? an alkyl group containing from 1 to 5 carbon atoms with the proviso that when X is hydrogen, R is an alkyl group containing at least 4 carbon atoms.

While all the phosphorus compounds designated in the above structural formula in which aromatic amine radicals are linked directly to the phosphorus atom in the molecule are useful in increasing the octane number of the fuel, it will be understood that the degree of their effectiveness may vary. Furthermore, the choice of the 3,060,009 Patented Oct. 23, 1962 specific compound or mixture of these compounds for use in the gasoline compositions of the invention will depend upon the cost of the compound and its solubility in gasoline.

In general, the solubility of the phosphoramides in gasoline increases in going from primary amines to secondary amines for the aromatic amine substituent in the molecule and in turn the phosphoramides with secondary amine radicals increase in solubility as the number of carbon atoms for the substituent X in the general formula is increased. Solubility of these compounds is also increased as the substituent R is increased in carbon atoms. Preferred compounds of the foregoing class for use in the fuel of the invention are N,N,N" triphenyl N,N',N" trimethyl-phosphoramide, N,N',N tri(p-butyl phenyl) phosphoramide, and N,N,N tri(p-amyl phenyl) phosphoramide.

The organo phosphoramides of the above designated class are compounds known to the art and methods for their preparation may be found in the literature. For example, N,N,N triphenyl N,N,N" tri-methylphosphoramide, a compound typical of the class of compounds represented by the foregoing general formula, may be prepared by reacting a pyridine complex of P001 with -methyl aniline in chloroform. The reaction proceeds according .to the following formula:

The amount of the phosphorarnide incorporated in the fuel of the invention depends to some extent upon the particular fuel employed, the amount of tetraethyl lead incorporated in the fuel, as Well as the particular phosphorus compound selected. It is preferred to express the amount of the compound to be added as the percent by weight of elemental phosphorus that is supplied to the fuel. It'has been found that the organic phosphoramides for the fuels of the present invention may be added to gasoline in amounts to provide from 0.0005% to 0.01% by weight phosphorus, but preferably fro-m 0.001% to 0.005% by weight phosphorus.

In addition to the organic phosphoramides, it is intended that the motor fuel of the invention may also include other known additives for commercial fuels, such as oxidation inhibitors, gum inhibitors, dyes, solvent oils, and the like. When :tetraethyl lead is used, the fuel may also contain a lead scavenging agent such as a volatile alkyl halide or a mixture of volatile alkyl halides such as ethylene dichloride and/0r ethylene dibromide. These halides are usually present as 1 theory of ethylene dichloride and /2 theory of ethylene dibromide (the socalled motor mix) or 1 theory of ethylene dibromide (the so-called aviation mix). By theory is meant the stoichiometric amount of the ethylene dihalide for combination with all of the lead as lead halide.

The base gasoline for the fuel can comprise a mixture of hydrocarbons boiling in the gasoline range and can be either .a straight-run gasoline or a gasoline obtained from a conventional cracking process, or mixtures thereof. The base gasoline may also contain components obtained from various other refinery processes, such as alkylation,

so that the pressure impulses from detonation can be detected; These are electronically amplified and their intensity indicated on a knock meter on the engine panel board. The motor fuels to be tested are used as the fuel for the engine. The test fuels are compared in knock intensity with that of various reference fuels which are blends of two standard compounds-iso-octane (2,2,4- trimethyl pentane) which is assigned an arbitrary number of 100 for the test, and n-heptane which is assigned an arbitrary number of 0. A blend of ise-octane and nheptane is \found which produces the same knock intensity as the fuel under test. The percentage by volume of isooctane in the matching blend is designated as the octane number of the gasoline. For example, if a blend of 80% iso-octane and 20% n-heptane is required to duplicate the knock intensity of the test fuel, the fuel would then be given an octane number of 80. The base gasoline was the same for all the fuels tested. Some of the fuels contained organic phosphoramides in accordance with the invention. For comparison, other fuels contained phosphorus compounds which have previously been proposed as gasoline additives and which are now in commercial usage. The base fuel had the following compositions and specifications:

Composition, vol. percent:

49.6 saturates 0.9 olefins 49.5 aromatics Octane No. (Research Method) 100.8

The results of the test are found in the table below:

Concentra- Change in Additive tion Per- Octane Octane Ratcentbywt. Rating ing Over Phosphorus Base Fuel Base Fuel None 100.8 N, ,N Triphenyl N,N,N trimethyl-phosphoramide 0. 0021 101.0 +0. 2 N,N,N" Tri(p-butyl phenyl) phosphoramide 0. 0021 101. 2 +0. 4 N,N',N Tri(p-amyl phenyl) phosphoramide 0. 0021 100. 9 +0. 1 Tricresyl Phosphate 0. 0021 100. 5 0. 3 Dimethyl Xylyl Phosphate 0. 0021 100. 6 0. 2

As will be noted from the above table, the addition of organophosphoramides to the base fuel offers a definite positive effect on octane number. By contrast, it is obvious that phosphate esters such as now in use for commercial gasolines demonstrate a definite negative efifect upon octane number.

The invention has been described hereinabove with reference to various specific examples and embodiments. It will be understood that the invention is not limited to such examples and embodiments but is intended to have such scope as aiforded by the appended claim.

We claim:

A leaded hydrocarbon fuel consisting essentially of a leaded gasoline and an octane increasing phosphorus additive selected from the group consisting of N,N,N" tri(pbutyl phenyl) phosphoramide and N,N,N tri(p-amyl phenyl) phosphorarnide in an amount sufiicient to supply from 0.0005 to 0.01% by weight phosphorus to said fuel.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,2118 Fry et al May 8, 1945 2,833,635 Hill et al May 6, 1958 2,860,958 Gilbert Nov. 18, 1958 2,863,743 Pellegrini et a1. Dec. 9, 1958 2,892,691 Howell June 30, 1959 2,897,068 Pellegrini et a1 July 28, 1959 OTHER REFERENCES Ind. and Eng. C-hem., March 1948, vol. 40, No. 3, Suitability of Gasolines as Fuels, by James of al., pp. 405-411.

Ind. and Eng. Chem, March 1951, vol. 43, No. 3, Antiknock Antagonist, by Livingston, pp. 663-670. 

